1. Field of the Invention
Embodiments of the invention generally relate to amorphous carbon films. More particularly, embodiments of the invention relate to hydrogenated diamond-like carbon (DLC) films for use as alignment films within a liquid crystal display (LCD).
2. Description of the Related Art
Active matrix liquid crystal displays (LCDs) are commonly used for applications such as computer and television monitors, cell phone displays, personal digital assistants (PDAs) and an increasing number of other devices. Generally, an active matrix LCD includes two glass plates having a layer of liquid crystal (LC) materials sandwiched therebetween. One of the glass plates typically includes a conductive film disposed thereon. The other glass plate typically includes an array of thin film transistors (TFTs) coupled to an electrical power source. Each TFT may be switched on or off to generate an electrical field between a TFT and the conductive film. The electrical field changes the orientation of the LC material to create a pattern on the LCD.
The LC material employed in the LCD typically relies on alignment layers to orient the LC material in a predetermined direction. The conventional method of LC material alignment includes placing a thin film of the LC material on a mechanically rubbed polyimide film deposited on a suitable substrate of the LCD. Rubbing of the polyimide film creates micro-grooves that the LC material aligns itself with. However, problems with this rubbing method include tracks formed in the polyimide, non-uniformity of the micro-grooves and debris from the cloth used to rub the polyimide. These problems degrade the LCD, necessitate extra cleaning steps and otherwise limit development of the LCD.
More recently, ion-beam treatment on diamond-like carbon (DLC) films used for the alignment of the LC material provides many advantages over conventional rubbed polyimide alignment films, such as, non-contact processing and alignment uniformity. Further, hydrogenated DLC films provide optical transparency suitable for use as the alignment film. Usually, plasma enhanced chemical vapor deposition (PECVD) followed by argon (Ar) ion beam irradiation forms the DLC films that are deposited for use as the alignment film. However, methods heretofore used have affected the desirability of the hydrogenated DLC for use as the alignment film within the LCD. Accordingly, it would be desirable to utilize process conditions that improve certain properties of the alignment film.
Thus, there exists a need for changes in the manufacture of an LCD for deposition of a hydrogenated amorphous carbon film, such as a hydrogenated DLC film, to provide an improved alignment film within the LCD.